Fighting a much more numerous enemy may seem stupid, but if you really believe your ideology, any odds of success are better than none. Think open-source developers competing with commercial offerings maintained by huge teams. Terrorists building IEDs when their enemy has a full military-industrial complex are much the same. They just really believe their ideology. On this, https://www.astralcodexten.com/p/your-book-review-nine-lives is a good read.
Embracing and believing this destructive ideology itself in the first place, when you could devote your life to so many better[1] things, is the sign of stupidity I mean.
Believing that God wants you to murder other people (heck, even babies) over things such as who's worshiping Him correctly... stupid.
1. Better for... you name it: Your quality of life, welfare of other human beings, economically, spiritually, environmentally.